.TH orthotest 1 "18 Feb 1997".SH NAMEorthotest \- see if a set of anisotropic elastic constants are orthorhombic.SH SYNOPSIS.BI "orthotest < elastic_constants.PP.B orthotestexpects to read from standard input an anisotropicelastic stiffness matrix in the form of 6 numbers on each of 6 lines of input.It finds the best-fitting orthorhombic medium to this,and outputs:.br0) the input anisotropic stiffness constants,.br1) the elastic constants rotated so that the best-fitting orthorhombicmatrix has the X, Y, and Z axes as principal axes,.br2) the orthorhombic approximation to the rotated matrix,.br3) the orthorhombic approximation in the original coordinate system,.br4) the percent difference between the input stiffness matrix and thebest-fittingorthorhombic approximation in the original coordinates (normalized bydividing each difference by the norm of the input stiffness matrix),.br5) the percent difference of the anisotropic elastic constantsfrom orthorhombic, and.br6) the coordinates of the 3 principle axes in the original coordinate system,in both cartesian and spherical notation..LPTheoretically,it is arbitrary how the three principal axes should be assigned to X, Y, and Z.This program tries each axis in turn to see how close it is to being an axis oftransversely isotropic (TI) symmetry.The axes are then reorderedso that the Z axis is the closest to being a TI axis of symmetry,then Y next closest, then X furthest.Thus, if the input medium is TI the Z axiswill always be chosen as the axis of symmetry.(Note that if the input medium is arbitrarily anisotropic, there isno reason to expect that the Z axis found by this program should preciselycoincide with the best-fitting TI axis found by the program titest.).LPSpherical coordinates are specified using phi and theta:.brphi=0 is the +Z axis.brphi=90 theta=0 is the +X axis.brphi=90 theta=90 is the +Y axis.LPFor more about what "best-fitting" means for elastic stiffness matrices, seethe article by Arts, Helbig, and Rasolofosaon in the SEG extended abstractsfor 1991, page 1534: "General Anisotropic Elastic Tensor in Rocks:Approximation, Invariants, and Particular Directions"..LPSee the.B titestman page for example input..SH OPTIONSCurrently there are no options or arguments..SH AUTHORThis program was written by Joe Dellinger at the Amoco Tulsa Technology Centerduring February 1997.This version is copyright (c) 2005 by the Societyof Exploration Geophysicists. For more information,see http://software.seg.org/2005/0001. You must read and accept theterms of usage in disclaimer.txt before use..SH SEE ALSO.BR titest (l)